/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * examples/kernel_sample/prioinherit.c
 *
 *   Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <stdio.h>
#include <unistd.h>
#include <semaphore.h>
#include <pthread.h>
#include <errno.h>

#ifdef CONFIG_ARCH_SIM
#  include <tinyara/arch.h>
#endif

#include "kernel_sample.h"

#if defined(CONFIG_PRIORITY_INHERITANCE) && !defined(CONFIG_DISABLE_SIGNALS) && !defined(CONFIG_DISABLE_PTHREAD)

/****************************************************************************
 * Definitions
 ****************************************************************************/

#ifndef CONFIG_SEM_PREALLOCHOLDERS
#  define CONFIG_SEM_PREALLOCHOLDERS 0
#endif

/* If resources were configured for lots of holders, then run 3 low priority
 * threads.  Otherwise, just one.
 */

#if CONFIG_SEM_PREALLOCHOLDERS > 3
#  define NLOWPRI_THREADS 3
#else
#  define NLOWPRI_THREADS 1
#endif

#ifndef CONFIG_SEM_NNESTPRIO
#  define CONFIG_SEM_NNESTPRIO 0
#endif

/* Where resources configured for lots of waiters?  If so then run 3 high
 * priority threads.  Otherwise, just one.
 */

#if CONFIG_SEM_NNESTPRIO > 3
#  define NHIGHPRI_THREADS 3
#else
#  define NHIGHPRI_THREADS 1
#endif

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

enum thstate_e {
	NOTSTARTED = 0,
	RUNNING,
	WAITING,
	DONE
};

static sem_t g_sem;
static volatile enum thstate_e g_middlestate;
static volatile enum thstate_e g_highstate[NHIGHPRI_THREADS];
static volatile enum thstate_e g_lowstate[NLOWPRI_THREADS];
static int g_highpri;
static int g_medpri;
static int g_lowpri;

/****************************************************************************
 * Name: nhighpri_waiting
 ****************************************************************************/

static int nhighpri_waiting(void)
{
	int n = 0;
	int i;

	for (i = 0; i < NHIGHPRI_THREADS; i++) {
		if (g_highstate[i] == WAITING) {
			n++;
		}
	}
	return n;
}

/****************************************************************************
 * Name: nhighpri_running
 ****************************************************************************/

static int nhighpri_running(void)
{
	int n = 0;
	int i;

	for (i = 0; i < NHIGHPRI_THREADS; i++) {
		if (g_highstate[i] != DONE) {
			n++;
		}
	}
	return n;
}

/****************************************************************************
 * Name: highpri_thread
 ****************************************************************************/

static void *highpri_thread(void *parameter)
{
	int threadno = (int)parameter;
	int ret;

	g_highstate[threadno - 1] = RUNNING;

	printf("highpri_thread-%d: Started\n", threadno);
	FFLUSH();
	sleep(1);

	printf("highpri_thread-%d: Calling sem_wait()\n", threadno);
	g_highstate[threadno - 1] = WAITING;
	ret                     = sem_wait(&g_sem);
	g_highstate[threadno - 1] = DONE;

	if (ret != 0) {
		printf("highpri_thread-%d: sem_take failed: %d\n", threadno, ret);
	} else if (g_middlestate == RUNNING) {
		printf("highpri_thread-%d: SUCCESS midpri_thread is still running!\n", threadno);
	} else {
		printf("highpri_thread-%d: ERROR --  midpri_thread has already exited!\n", threadno);
	}

	sem_post(&g_sem);
	printf("highpri_thread-%d: Okay... I'm done!\n", threadno);
	FFLUSH();
	return NULL;
}

/****************************************************************************
 * Name: hog_cpu
 ****************************************************************************/

static inline void hog_cpu(void)
{
#ifdef CONFIG_ARCH_SIM
	/* The simulator doesn't have any mechanism to do asynchronous pre-emption
	 * (basically because it doesn't have any interupts/asynchronous events).
	 * The simulator does "fake" a timer interrupt in up_idle() -- the idle
	 * thread that only executes when nothing else is running.  In the simulator,
	 * we cannot suspend the middle priority task, or we wouldn't have the
	 * test that we want.  So, we have no option but to pump the fake clock
	 * here by calling up_idle().  Sigh!
	 */

	up_idle();
#else
	/* On real platforms with a real timer interrupt, we really can hog the
	 * CPU.  When the sleep() goes off in priority_inheritance(), it will
	 * wake up and start the high priority thread.
	 */

	volatile int i;
	for (i = 0; i < INT_MAX; i++);
#endif
}

/****************************************************************************
 * Name: medpri_thread
 ****************************************************************************/

static void *medpri_thread(void *parameter)
{
	printf("medpri_thread: Started ... I won't let go of the CPU!\n");
	g_middlestate = RUNNING;
	FFLUSH();

	/* The following loop will completely block lowpri_thread from running.
	 * UNLESS priority inheritance is working.  In that case, its priority
	 * will be boosted.
	 */

	while (nhighpri_running() > 0) {
		hog_cpu();
	}

	printf("medpri_thread: Okay... I'm done!\n");
	FFLUSH();
	g_middlestate = DONE;
	return NULL;
}

/****************************************************************************
 * Name: lowpri_thread
 ****************************************************************************/

static void *lowpri_thread(void *parameter)
{
	void *retval = (void *)-1;
	struct sched_param sparam;
	int threadno = (int)parameter;
	int expected;
	int count;
	int policy;
	int ret;
	int nwaiting = 0;
	int i;

	g_lowstate[threadno - 1] = RUNNING;
	printf("lowpri_thread-%d: Started\n", threadno);

	ret = pthread_getschedparam(pthread_self(), &policy, &sparam);
	if (ret != 0) {
		printf("lowpri_thread-%d: ERROR pthread_getschedparam failed: %d\n", threadno, ret);
	} else {
		printf("lowpri_thread-%d: initial priority: %d\n", threadno, sparam.sched_priority);
		if (sparam.sched_priority != g_lowpri) {
			printf("               ERROR should have been %d\n", g_lowpri);
		}
	}

	g_lowstate[threadno - 1] = WAITING;
	ret = sem_wait(&g_sem);
	if (ret != 0) {
		printf("lowpri_thread-%d: sem_take failed: %d\n", threadno, ret);
	} else {
		/* Hang on to the thread until the middle priority thread runs */

		while (g_middlestate == NOTSTARTED && nhighpri_waiting() < NHIGHPRI_THREADS) {
			printf("lowpri_thread-%d: Waiting for the midle pri task to run\n", threadno);
			printf("    g_middlestate:  %d\n", (int)g_middlestate);
			for (i = 0; i < NHIGHPRI_THREADS; i++) {
				printf("    g_highstate[%d]: %d\n", i, (int)g_highstate[i]);
			}
			printf("    I still have a count on the semaphore\n");
			sem_enumholders(&g_sem);
			FFLUSH();
			sleep(1);
		}

		/* Account for all of the semaphore counts.  At any given time if there are 'n'
		 * running hight prioity tasks, then the semaphore count should be '-n'
		 */

		sched_lock(); /* Needs to be atomic */
		ret      = sem_getvalue(&g_sem, &count);
		nwaiting = nhighpri_waiting();
		sched_unlock();

		if (ret < 0) {
			printf("lowpri_thread-%d: ERROR sem_getvalue failed: %d\n", threadno, errno);
		}
		printf("lowpri_thread-%d: Sem count: %d, No. highpri thread: %d\n", threadno, count, nwaiting);

		/* The middle priority task is running, let go of the semaphore */

		if (g_middlestate == RUNNING && nwaiting == -count) {
			/* Good.. the middle priority task is still running and the counts are okay. */

			retval = NULL;
		} else {
			/* If the sem count is positive, then there all of the higher priority threads
			 * should have already completed.
			 */

			printf("lowpri_thread-%d: %s the middle priority task has already exitted!\n",
				   threadno, count >= 0 ? "SUCCESS" : "ERROR");
			printf("               g_middlestate:  %d sem count=%d\n", (int)g_middlestate, count);
			for (i = 0; i < NHIGHPRI_THREADS; i++) {
				printf("               g_highstate[%d]: %d\n", i, (int)g_highstate[i]);
			}
		}
	}

	ret = pthread_getschedparam(pthread_self(), &policy, &sparam);
	sem_enumholders(&g_sem);
	sem_post(&g_sem);
	if (ret != 0) {
		printf("lowpri_thread-%d: ERROR pthread_getschedparam failed: %d\n", threadno, ret);
	} else {
		if (nwaiting > 0) {
			expected = g_highpri;
		} else {
			expected = g_lowpri;
		}

		printf("lowpri_thread-%d: %s priority before sem_post: %d\n",
			   threadno,
			   sparam.sched_priority != expected ? "ERROR" : "SUCCESS",
			   sparam.sched_priority);

		if (sparam.sched_priority != expected) {
			printf("               ERROR should have been %d\n", expected);
		}
	}

	ret = pthread_getschedparam(pthread_self(), &policy, &sparam);
	if (ret != 0) {
		printf("lowpri_thread-%d: ERROR pthread_getschedparam failed: %d\n", threadno, ret);
	} else {
		printf("lowpri_thread-%d: %s final priority: %d\n",
			   threadno,
			   sparam.sched_priority != g_lowpri ? "ERROR" : "SUCCESS",
			   sparam.sched_priority);

		if (sparam.sched_priority != g_lowpri) {
			printf("               ERROR should have been %d\n", g_lowpri);
		}
	}
	sem_enumholders(&g_sem);

	printf("lowpri_thread-%d: Okay... I'm done!\n", threadno);
	FFLUSH();
	g_lowstate[threadno - 1] = DONE;
	return retval;
}
#endif /* CONFIG_PRIORITY_INHERITANCE && !CONFIG_DISABLE_SIGNALS && !CONFIG_DISABLE_PTHREAD */

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: priority_inheritance
 ****************************************************************************/

void priority_inheritance(void)
{
#if defined(CONFIG_PRIORITY_INHERITANCE) && !defined(CONFIG_DISABLE_SIGNALS) && !defined(CONFIG_DISABLE_PTHREAD)
	pthread_t lowpri[NLOWPRI_THREADS];
	pthread_t medpri;
	pthread_t highpri[NHIGHPRI_THREADS];
	pthread_addr_t result;
	pthread_attr_t attr;
	struct sched_param sparam;
	int my_pri;
	int status;
	int i;

	printf("priority_inheritance: Started\n");

	g_middlestate = NOTSTARTED;
	for (i = 0; i < NHIGHPRI_THREADS; i++) {
		g_highstate[i] = NOTSTARTED;
	}
	for (i = 0; i < NLOWPRI_THREADS; i++) {
		g_lowstate[i]  = NOTSTARTED;
	}

	status = sched_getparam(getpid(), &sparam);
	if (status != 0) {
		printf("priority_inheritance: sched_getparam failed\n");
		sparam.sched_priority = PTHREAD_DEFAULT_PRIORITY;
	}
	my_pri  = sparam.sched_priority;

	g_highpri = sched_get_priority_max(SCHED_FIFO);
	g_lowpri = sched_get_priority_min(SCHED_FIFO);
	g_medpri = my_pri - 1;

	sem_init(&g_sem, 0, NLOWPRI_THREADS);
	dump_nfreeholders("priority_inheritance:");

	/* Start the low priority threads */

	for (i = 0; i < NLOWPRI_THREADS; i++) {
		int threadno = i + 1;
		printf("priority_inheritance: Starting lowpri_thread-%d (of %d) at %d\n",
			   threadno, NLOWPRI_THREADS, g_lowpri);
		status = pthread_attr_init(&attr);
		if (status != 0) {
			printf("priority_inheritance: pthread_attr_init failed, status=%d\n", status);
		}
		sparam.sched_priority = g_lowpri;
		status = pthread_attr_setschedparam(&attr, & sparam);
		if (status != OK) {
			printf("priority_inheritance: pthread_attr_setschedparam failed, status=%d\n", status);
		} else {
			printf("priority_inheritance: Set lowpri_thread-%d priority to %d\n",
				   threadno, sparam.sched_priority);
		}

		status = pthread_create(&lowpri[i], &attr, lowpri_thread, (void *)threadno);
		if (status != 0) {
			printf("priority_inheritance: pthread_create failed, status=%d\n", status);
		}
	}
	printf("priority_inheritance: Waiting...\n");
	sleep(2);
	dump_nfreeholders("priority_inheritance:");

	/* Start the medium priority thread */

	printf("priority_inheritance: Starting medpri_thread at %d\n", g_medpri);
	status = pthread_attr_init(&attr);
	if (status != 0) {
		printf("priority_inheritance: pthread_attr_init failed, status=%d\n", status);
	}

	sparam.sched_priority = g_medpri;
	status = pthread_attr_setschedparam(&attr, & sparam);
	if (status != OK) {
		printf("priority_inheritance: pthread_attr_setschedparam failed, status=%d\n", status);
	} else {
		printf("priority_inheritance: Set medpri_thread priority to %d\n", sparam.sched_priority);
	}
	FFLUSH();

	status = pthread_create(&medpri, &attr, medpri_thread, NULL);
	if (status != 0) {
		printf("priority_inheritance: pthread_create failed, status=%d\n", status);
	}
	printf("priority_inheritance: Waiting...\n");
	sleep(1);
	dump_nfreeholders("priority_inheritance:");

	/* Start the high priority threads */

	for (i = 0; i < NHIGHPRI_THREADS; i++) {
		int threadno = i + 1;
		printf("priority_inheritance: Starting highpri_thread-%d (of %d) at %d\n",
			   threadno, NHIGHPRI_THREADS, g_highpri);
		status = pthread_attr_init(&attr);
		if (status != 0) {
			printf("priority_inheritance: pthread_attr_init failed, status=%d\n", status);
		}

		sparam.sched_priority = g_highpri - i;
		status = pthread_attr_setschedparam(&attr, & sparam);
		if (status != OK) {
			printf("priority_inheritance: pthread_attr_setschedparam failed, status=%d\n", status);
		} else {
			printf("priority_inheritance: Set highpri_thread-%d priority to %d\n",
				   threadno, sparam.sched_priority);
		}
		FFLUSH();

		status = pthread_create(&highpri[i], &attr, highpri_thread, (void *)threadno);
		if (status != 0) {
			printf("priority_inheritance: pthread_create failed, status=%d\n", status);
		}
	}
	dump_nfreeholders("priority_inheritance:");
	FFLUSH();

	/* Wait for all thread instances to complete */

	for (i = 0; i < NHIGHPRI_THREADS; i++) {
		printf("priority_inheritance: Waiting for highpri_thread-%d to complete\n", i + 1);
		FFLUSH();
		(void)pthread_join(highpri[i], &result);
		dump_nfreeholders("priority_inheritance:");
	}
	printf("priority_inheritance: Waiting for medpri_thread to complete\n");
	FFLUSH();
	(void)pthread_join(medpri, &result);
	dump_nfreeholders("priority_inheritance:");
	for (i = 0; i < NLOWPRI_THREADS; i++) {
		printf("priority_inheritance: Waiting for lowpri_thread-%d to complete\n", i + 1);
		FFLUSH();
		(void)pthread_join(lowpri[i], &result);
		dump_nfreeholders("priority_inheritance:");
	}

	printf("priority_inheritance: Finished\n");
	sem_destroy(&g_sem);
	dump_nfreeholders("priority_inheritance:");
	FFLUSH();
#endif /* CONFIG_PRIORITY_INHERITANCE && !CONFIG_DISABLE_SIGNALS && !CONFIG_DISABLE_PTHREAD */
}
